Bugs

Yes if they are gnats, they will eat the organic matterlike roots and soil. I tried to get control of them with mosquito bites, but never got control. They multiply very quickly. You can put sand as a top layer and water from the bottoms. Butt chugg as some call it . Not to scare you but I never had any luck. I think there were too many before I noticed them. You got to love buying dirt with an insect farm in them. I hate those fuckers so bad I went to DWC and have not looked back. We have them bad here in the south. Others may have success fighting them off hopefully they will chime in. Rabbit might have some good ideas.

the way to prevent fungus gnats is to keep them from a damp medium. One thing you can do is cover the soil with paper plates.

Hydroponic growing isnt immune either! They will find the water source and go right into the clay pebbles to mate. as long as they can find a moist environment!  (freshly watered soil/ coco / a wet block of rockwool / a cup of water. They are all a perfect environment for fungus gnats) I have even seen them make their way INTO my buckets!

sticky traps help. Ladybugs can help. but you still need to isolate them from that moist environment